110 Scientific Proceedings, Royal Dublin Society. 
dissolved in dilute hydrochloric acid which had previously been 
employed for finally rinsing out the balloon (in order to dissolve 
any barium carbonate adhering to its sides). The solution was 
then precipitated with sodium sulphate and the resulting barium 
sulphate washed and dried on a sand bath. Throughout these 
operations no filter was used—all washings being by decantation. 
To describe even in outline all the different processes which have 
been employed since De Saussure’s time to determine atmospheric 
carbonic anhydride would not only be tedious but would scarcely 
serve any useful purpose. But, on the other hand, certain of 
these processes deserve notice, owing to the importance of the 
work performed by their aid. With the exception of one or two 
methods based on the physical properties of gases, such as absorp- 
tion of heat,! rate of diffusion,’ &c., all these processes depend in 
the first instance on the employment of an alkali or alkaline earth 
as absorbent; the amount of carbonic anhydride absorbed being 
arrived at subsequently by one or other of several methods, among 
which the more important are :— 
(1.) Increase in the weight of-the absorbing apparatus. 
(2.) Determination of the excess of the absorbent. 
(3.) Liberation and measurement of the absorbed carbonic 
anhydride. 
Quite a number of observers have made use of the first method, 
which appears to have been inaugurated by C. Brunner’: his. 
absorbing apparatus consisting of a tube filled partly with slaked 
lime, and partly with asbestos moistened with sulphuric acid to 
absorb any moisture which might ‘be lost from the lime. Bous- 
singault* employed pumice moistened with potash solution ; 
Schlagintweit,’ solid potash; Ch. Méne,’ potash solution in Liebig’s 
bulbs; Claésson,’ barium hydrate. 
1 Rontgen, ‘‘ Ber. d. oberhessischen Ges. f. Natur. u. Heilkunde,” 20 [1881]; 
p- 52. Heine, ‘‘ Wiedemann’s Annalen,’’ 16 [1882], p. 441. 
2 Schydlowski, ‘‘ Zeitschr. f. anal. Chem.,’’ 27 [1888], p. 720. 
3 Brunner, ‘‘ Pogg. Annalen,’’ 24 [1832], p. 569, and “‘ Annales de Chimie et de 
Phys.,’’ [3], 3 [1841], p. 306. 
4 Boussingault, ‘‘ Annales de Chimie et de Phys.,’’ [8], 10, [1844], p. 456. 
5 Schlagintweit, ‘‘ Poge. Annalen,’’ 76 [1849], p. 446. 
6 Mene, ‘‘ Compt. Rend.,”’ 33 [1851], p. 39. 
7 Claésson, “‘ Ber. d. deutsch. chem. Ges.,’’ 9 [1876], p. 174. 
